3,5-Dichloro-2-pyridoxyethyl ethers as herbicides

ABSTRACT

3,5-Dichloro-2-pyridoxyethyl hydrocarbon ether having the structure:   WHERE R is an aliphatic or aromatic radical, is used as a preemergent herbicide for crops by applying to the soil, a weed phytotoxic amount of the ether prior to the emergence of the food crop plants.

United States Patent [1 1 Whitaker et a1.

[ July 15, 1975 3,5-DICHLORO-2-PYRIDOXYETHYL ETHERS AS HERBICIDES [75] inventors: Reginald L. Whitaker, Tacoma,

Wash.; Herbert Q. Smith, Malvern, Pa.

[73] Assignee: Pennwalt Corporation, Philadelphia,

[22] Filed: Feb. 13, 1974 [21] App]. No.: 442,018

Related U.S. Application Data [60] Division of Ser. No. 284,316, Aug. 28, 1972, Pat. No. 3,814,774, which is a continuation-in-part of Ser. No. 115,707, Feb. 16, 1971, abandoned.

3,251,849 5/1966 Tomita 71/94 3,291,804 12/1966 Johnston et a1 71/94 3,455,938 7/1969 Blair et a1. 71/94 3,682,938 8/1972 Troxel et a1. 71/94 Primary Examiner-Glennon 1-1. Hollrah Attorney, Agent, or Firm-Robert G. Danehower 5 7 ABSTRACT 3,5-Dichloro-Z-pyridoxyethyl hydrocarbon ether having the structure:

ocn cn oxzwhere R is an aliphatic or aromatic radical, is used as a pre-emergent herbicide for crops by applying to the soil, a weed phytotoxic amount of the ether prior to the emergence of the food crop plants.

9 Claims, No Drawings 1 3,5-DICHLORO-Z-PYRIDOXYETHYL ETHERS AS I-IERBICIDES This application is a divisional case out of Ser. No. 284,316, filed 8/28/72 now US. Pat. No. 3,814,774. Ser. No. 284,316 was a continuation in part application of Ser. No. 115,707, filed February 16, 1971 and now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention:

This invention relates to herbicidal compositions and methods for their utilization for controlling the growth of weeds. More particularly, this invention relates to 3,5-dichloro-2-pyridoxyethyl ethers and their use as a pre-emergence herbicide for controlling weeds.

2. Description of the Prior Art:

A pre-emergence herbicide is a compound that destroys or prevents the growth of a wide variety of weeds and other unwanted vegetation without damaging the sought after crop, e.g., does not inhibit the emergence or retard the growth of a food crop.

Pyridine compounds have been used as plant growth regulators and pre-emergence herbicides. However, the relationship between the structure of the pyridine compound and its herbicidal activity is undefined. Often, pyridine compounds retard the pre-emergence of crop seeds to the same degree they do the weed seeds. For example; in US. Pat. No. 3,249,419, at column 8, a table discloses the results of treatment of flats containing seeds of crop plants and weeds with hydroxyhalopyridines. The table indicates that 90 to 100 percent of food crop seeds failed to germinate at the lowest dosage indicated.

H. Veldstra in Chemistry and Mode of Action Plant Growth Substances (London, 1955) pages 129 to 130, discusses the activity of pyridine compounds in promoting or influencing the growth of certain food crops. In particular, 3,5-dichloro-Z-pyridoxyacetic acid is shown to have activity approaching the level of indoleacetic acid. However, this discussion was directed to the relationship between the pyridine compounds structure and activity in influencing plant growth, i.e., their effect on established plants. Their activity as preemergence herbicides is undiscussed, and accordingly, the relationship between the structure of pyridine compounds and their activity as pre-emergent herbicides is not established by Veldstra.

SUMMARY OF THE INVENTION Theinvention sought to be patented in its composition aspect is described as residing in the concept of a chemical compound having a molecular structure of the 3,5-dichloro-2-pyridoxyethyl nucleus to which there is attached a hydrocarbon oxide radical (OR), as is shown in the following structure:

CPL

The invention sought to be patented in its process of using aspect resides in the concept of administering to soil, prior to the emergence of crops therefrom, a weed phytotoxic amount of a composition of matter having a molecular structure in which a hydrocarbon oxide radical is attached to the ethyl radical of a 3,5-dichloro- 2-pyridoxyethyl nucleus as the essential active ingredient of a pre-emergence formulation for the suppression of weeds in the soil.

The embodiments of the composition aspect of the invention possess the inherent general property of solubility in many organic solvents and aqueous acid solutions from which the acid salts may be obtained on evaporation of the water. Examination of the compounds produced according to the hereinafter described process with ultra-violet and infra-red spectographic analysis, yields spectral data confirming molecular structure hereinbefore set forth. The aforementioned physical characteristics taken together with the nature of the starting materials and the mode of synthesis positively confirm the structure of the composition sought to be patented. As used herein, the term hydrocarbon oxide, OR means wherein the hydrocarbon R contains from one to 18 carbon atoms and is alkyl including cycloalkyl, alkenyl, alkynyl, haloalkyl, haloalkenyl, haloalkylyl, wherein one or more halogen atom is present, aryl and aralkyl.

DESCRIPTION OF THE PREFERRED EMBODIMENT More preferred is the embodiment of the 3,5-dichloro-2-pyridoxyethyl nucleus having a hydrocarboxide radical, OR, wherein the R group is selected from the group consisting of alkyl, haloalkyl, alkenyl and haloalkenyl. As used throughout this specification and in the claims the term alkyl is meant to include cycloalkyl. Haloalkyl and haloalkenyl is intended to include polyhalogenated alkyl and alkenyl radicals.

Most preferred is the embodiment of the 3,5-dichloro-2-pyridoxyethyl nucleus having a hydrocarbon oxide radical, OR, wherein the R group is selected from the group consisting of alkyl and chlorinated alkyl. The term chlorinated alkyl includes compounds having 1 to 6 chlorine atoms on the alkylradical.

The manner and process of making and using the invention will now be generally described so as to enable a person skilled in the art of chemistry to make and use the same, as follows:

The 2,3,5-trichloropyridine employed as a starting material for the preparation of the physical embodiments of the composition aspect of our invention is generally known or readily prepared by procedures known to those skilled in the art.

According to one procedure, the physical embodiment of our concept is made by reacting 2,3,5- trichloropyridine with an alkali metal salt of a mono ether of ethylene glycol wherein the mono ether bearsE an R group desired on the ether oxygen of the composition of the invention. This reaction is shown as follows:

c C1 a-o-cu on o-mmu Metal- N/ o-ou -cu -orz alka11 metal chloride.

The reactants are mixed together without a solvent and heated above room temperature generally about 50C with a trace amount of copper powder. Usually, an exothermic reaction occurs causing the temperature of the reaction mixture to rise about 100C.

In another procedure, the alkali metal salt is allowed to react with 2,3,5-trichloropyridine in the presence of a solvent. The reaction is carried out at reflux for several hours. The alkali metal salt of the mono ether of ethylene glycol is prepared by treating the mono ether of ethylene glycol with an alkali metal hydride, e.g., sodium hydride, in an inert solvent such as tetrahydrofuran or with an alkali metal tertiary alkoxide, e.g., potassium tertiary butoxide in a polar solvent such as tertiary butanol.

The R group of the 3,5-dichloropyridoxy ethyl ether can also be reacted with chemicals in order to introduce additional substituents onto the R group. For example, when the R group is an ally] radical, it may be chlorinated to produce 3,S-dichloropyridoxyethyl 2,3- dichloropropyl ether. Similarly, when the R group is phenyl, benzyl or substituted benzyl, then reactions may be carried out on the phenyl or benzyl portion of the 3,5-dichloropyridoxyethyl ether in order to further modify the structure of the R group.

The ethylene radical bridging the 3,5-pyridoxy group and the OR group is shown in the above structural formula without substituents. However, it is apparent that lower alkyl substituents may be placed on one or both of its carbon atoms to form homologues of the present invention.

The following examples are illustrative of the methods employed to prepare the compounds.

EXAMPLE 1 3,5-DICHLORO-2-[ Z-PHENOXY )ETHOXY ]PYRI- DINE.

Prepare a suspension of 4.4 grams (0.11 moles) of sodium hydride in 50 milliliters of tetrahydrofuran using a 60 percent mixture of sodium hydride in oil. Add a solution of 13.8 grams (0.10 moles) of 2- phenoxyethanol in 50 milliliters of tetrahydrofuran to the sodium hydride suspension. An exothermic reaction occurs accompanied by hydrogen being evolved. Stir the resulting suspension for three hours after the addition is completed. Evaporate the tetrahydrofuran with a stream of nitrogen gas until a powdery residue remains. Add 18.3 grams (0.10 moles) of 2,3,5- trichloropyridine and 0.3 grams of copper powder to the residue. Stir the mixture and heat gently to 50C until an exothermic reaction occurs causing a slow temperature rise to 100C. Then a more rapid temperature rise to 180C. Maintain the temperature at 180C. for one hour and cool to ambient temperature. Dissolve the product in 250 milliliters of methylene chloride, filter to remove solids and concentrate the filtrate in vacuo to a viscous semisolid residue. Recrystallization of the residue from petroleum ether including treatment with decolorizing charcoal yields about 19 grams of 3,5-dichloro-2[(2-phenoxy)ethoxy]pyridine melting at 40-42C.

Analysis Calculated C, 54.95; H, 3.90; Cl, 24.96; N, 4.93.

Found C, 55.39; H, 4.06; C1, 24.91; N, 4.78.

EXAMPLE 2 3,5-D1CHLORO-2-[(2-ALLYLOXY)ETHOXY]- PYRIDINE Follow the procedure of Example 1 using 10.2 grams of 2-allyloxyethanol in place of the 2-phenoxyethanol. Distill the residue remaining after evaporation of the methylene chloride through a 4 inch helix-packed column. The product is a liquid, boilling point 8780C/0.55 millimeters of mercury, n 1.5278. Analysis Calculated C, 48.40; H, 4.47; Cl, 28.58; N, 5.56.

Found C,48.49; H, 4.47;Cl,28.32; N, 5.52.

EXAMPLE 3 3,5-DICHLORO-2-[(2-ET1-lOXY)ETHOXY]PYRl- DlNE Follow the procedure of Example 1 using 9.0 grams of ethylene glycol monoethyl ether in place of the 2- phenoxy ethanol. Distill the residue from the methylene chloride evaporation through a 4 inch column packed with glass helices. The product distills at about 76-78C/0.05 millimeters of mercury, n 1.210. Analysis Calculated C, 45.90; H, 4.76; CI, 29.69; N587.

Found C, 45.78; H, 4.70; C], 30.04; N. 5.93.

EXAMPLE 4 3,5-DICHLORO-2-[(2-BENZYLOXY)ETl-1OXY]- PYRIDINE Follow the procedure of Example 1 using 0.1 moles of 2-benzyloxyethanol. Distill the product through a 4 inch helix-packed column. The product is a liquid boiling 138142C/0.05 millimeters of mercury, n 1.5643. Analysis Calculated C, 56.39; H, 4.39; Cl, 23.79; N. 4.70.

Found C, 56.97; H, 4.45; CI, 22.78; N. 4.81.

EXAMPLE 5 3,5-DICHLORO-2-[(2-METHOXY)ETHOXL]PYR1- DlNE Add 7.6 grams (0.10 moles) of ethylene glycol monomethyl ether to 11.2 grams (0.10 moles) of potassium tertiary-butoxide in milliliters of tertiary butanol. Then add 18.3 grams (0.10 moles) of 2,3,5- trichloropyridine and reflux for 20 hours. Cool, filter off the solid residue which deposits and wash the residue with 50 milliliters of ethyl ether. Combine the ether washings and the filtrate and concentrate in a vacuum to a semi-solid liquid. Take the semi-solid liquid up in 100 milliliters of hexane and filter off the insoluble residue. Concentrate the filtrate in vacuum and distill the oil residue through a 4 inch helix-packed column. The product boils 78-81C at 0.10 milliliters of mercury, n 1.5320. On standing, the product crystallizes to a solid melting 3637C. Analysis Calculated C, 43.26; H, 4.08; Cl, 31.93.

Found C, 43.47; H, 4.12; Cl, 31.97.

EXAMPLE 6 3 ,5-DlCHLORO-2-[ (Z-PROPOXY )ETHOXY1PYRI- DINE Follow the procedure of Example 5 using 10.4 grams (0.1 moles) of 2-(n-propoxy)ethanol in place of the monomethyl ether of ethylene glycol. Distill the product through a 4 inch helix-packed column. The product boils at 88-90C/0.08 millimeters of mercury, n 1.5148. Analysis Calculated C, 48.02; H, 5.24; Cl, 28.35; N, 5.60.

Found C, 47.90; H, 5.10; Cl, 27.98; N, 5.62.

EXAMPLE 7 3,5-DlCHLORO-2-[(2-BUTOXY)ETHOXY]PYRI- DINE Follow the procedure of Example 5 using 1 1.8 grams (0.1 mole) of the mono-n-butyl ether of ethylene glycol in place of the monomethyl ether of ethylene glycol. Distill the product through a 4 inch helix-packed column. The product boils 98-100C/0.05 millimeters of mercury, n 1.5118. Analysis Calculated C, 50.01; H, 5.72; Cl, 26.85.

Found C, 49.85; H, 5.48; C1, 27.89.

EXAMPLE 8 3,5-DlCHLORO-2-[(2-DODECYLOXY) ETHOXY]- PYRIDINE Follow the procedure of Example 5 using 23.0 grams (0.10 moles) of 2-(dodecyloxy)-ethanol in place of the monomethyl ether of ethylene glycol. The product after the evaporation of the solvent is a solid. Recrystallize the solid from 95% ethanol. The product is a solid melting 3335C. Analysis Calculated C, 60.63; 2h, .30u N, 3.72.

Found c, 60.64$ 0h, 816$ N, 3.77.

EXAMPLE 9 3,5-DlCHLORO-2-[2-(2-Chloroallyloxy)ethoxy]- PYRlDlNE Follow the procedure of Example using 13.7 grams (0.1 mole) of 2-(2-chloroallyloxy)ethanol in place of the monomethyl ether of ethylene glycol. Distill the product. The product is a liquid boiling 113-l15C/0.l0 millimeters of mercury, n 1.5483. Analysis Calculated C, 42.50; H, 3.57; N, 4.96.

Found C, 42.55; H, 3.73; N, 5.01.

EXAMPLE l0 3,5-DlCHLORO-2-[2,3-DICHLOROPROPOXY)E- THOXY]PYR1DINE Dissolve 24.8 grams (0.1 mole) of 3,5-dichloro-2-[2- (allyloxy)ethoxy]pyridine in 250 milliliters of carbon tetrachloride cooled to 5C. Slowly bubble chlorine gas into this solution for minutes. The temperature rises to 12C at this point. Continue chlorination for 4 hours at 5-10C. Remove excess chlorine by passing nitrogen gas into the carbon tetrachloride solution. Then evaporate the carbon tetrachloride in vacuum. Distill the product through a simple distillation apparatus at 0.1 millimeters. The product boils at 140143C/0.1 millimeters of mercury, n 1.5442. Analysis Calculated C, 37.64; H, 3.48; Cl, 44.46.

Found C, 37.43; H, 3.58; Cl, 44.13.

EXAMPLE 1 l 3,5-DlCHLORO-2-[2-(2,2,3-

TR lCHLOROPROPOXY )ETHOXY PYRIDINE Dissolve 27.29 (0.095 moles) of the 3,5-dichloro-2- (2-[2-chloroallyloxy)ethoxy]pyridine of Example 9 in 250 ml. of carbon tetrachloride and cool to 5C. Slowly pass chlorine gas into the solution. The temperature of the solution may rise to 10C. Introduce chlorine gas for 5 hours while allowing the solution to warm to room temperature. Flush the solution of unreacted chlorine by passing nitrogen gas into the solution and evaporate the carbon tetrachloride under vacuum. Distill the resulting pale amber liquid and vacuum. The resulting product distills at a temperature of l53-156C at 0.20 mm. of mercury pressure, n 1.5528. Analysis Calculated C, 33.03; H, 2.72; Cl, 51.27.

Found C, 33.98 H, 2.85; Cl, 50.16.

EXAMPLE l2 3,5-DlCHLORO-2-[(Z-CYCLOHEXYLOXY)E- THOXYlPYRIDlNE To a stirred solution of 4.5 g (0.04 mole) of potassium tertiary-butoxide in 50 ml of tertiary butyl alcohol was added 5.8 g (0.04 mole) of 2-(cyclohexyloxy)ethanol. After 15 min was added 7.3 g (0.04 mole) of 2,3,5-trichloropyridine in 25 ml of tertiary butyl alcohol. After refluxing for 25 hrs., the solid was filtered off and washed with three 50 ml portions of diethyl ether. The combined filtrate and washings were concentrated in vacuum and the liquid residue distilled to afford 4.0 g (34% conversion) of colorless liquid, b.p. l72176 (3.2 mm), n 1.5280.

' By following the procedures of the examples, additional 3,S-dichloropyridoxyethyl hydrocarbon ethers may be prepared.

According to the method of using the compounds of this invention as pre-emergence herbicides, an amount of 3,5-dichloropyridoxyethyl hydrocarbon ether which is phytotoxic to weed seeds is applied to soil implanted with crop seeds. The weed-phytotoxic amount employed varies from about 0.1 to about 10 pounds per acre. Preferably about 0.25 to about 4 pounds per acre is employed. Amounts larger than 10 pounds per acre are also effective to prevent the emergence of weed seeds; however, larger amounts are uneconomical and may tend to damage the crop seeds.

The composition aspect of this invention may be formulated for application as a dispersion in water or organic solvents or as a solution in organic solvents. The latter solutions can be formulated as dispersion in water with an ionic, cationic or nonionic surfactants. These surfactants also have the advantage that their presence aids penetration of the compound into plant seed and soil surfaces. Suitable water dispersions may be prepared with or without surfactants by ball milling or other fine grinding processes. The composition may also be formulated as a suspension using suspending agents such as lignin sulfonates, bentonite, dilute solutions of methocel and the like.

It is often desired to prepare an emulsion concentrate which is mixed with water in the field. These emulsion concentrates are prepared by dissolving the composition aspect of the invention with suitable organic solvents which are immiscible in water, such as xylene, naphtha solvents, isophorone, benzene, heptane, heavy mineral oils, kerosene and thereafter adding a surfactant. Surfactants suitable for dispersing the compounds are described in Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd edition Volumne 19, pages 507-593.

The concentration of the pre-emergence weed control aspect of the invention in crop production involves applying the 3,5-dichloro-Z-pyridoxyethyl hydrocarbon ether to the soil prior to the emergence of the food crop from the soil. The application may be made at the same time as the seeding operation and most commonly involves the use of a sprayer or granular applicator attached to the planter. The pre-emergence compound is applied to the soil surface immediately after covering tion were evaluated for pre-emergence weed control efficacy relative to the production of crops. In addition, their performance was compared to that of the structurally analogous 3,5-dichloro-Z-pyridoxyacetic acid.

the crop seed. As desired, the application may be a nar- The following Table 1 summarizes experiments perrow band immediately in the vicinity of the planted formed showing the pre-emergence herbicidal activity food p seed or the entire area y be treated Addiof the composition aspect of this invention. The comtionally the chemical may be mixed with the top layer pound employed is formulated in solvents and thereafof the soil at the time of application using suitable ter the solution is dispersed in water and sprayed on the equipment. 10 soil surface of a prepared flat containing crop seeds and The compounds of this invention possess the necesweed seeds. sary properties to be effective in field use. They have The formulation may be, for example, a 10 percent a wide spectrum of weed control which is desirable besolution of the compound in xylene, or diacetone alcocause the food crops can be vested with many species hol which solvent may also contain a surfactant such as of grasses and broad leaf weeds. Another important Triton X-l6l. Other formulations may includea 1% soproperty is the lack of significant vital toxic activity tolution of the compound in a 1:1 solution of acetone and wards food crops. This is an important consideration diacetone alcohol. The choice of solvent is dictated by because it is impossible under field conditions to comthe individual solubility characteristics of the completely maintain a separation of the chemical from the pound. crop seed and it is necessary that the compounds be The method followed is to use V2 square foot flat able to prevent the germination of weed seeds without seeded on the surface with the indicated weeds and significantly affecting the crop seeds. Chemicals which planted with the indicated crops. A formulation of the perform this way must have unique and specific properchemical dispersed in water is sprayed on the soil surties since some of the commercial crop plants are boface and the flat held on the greenhouse bench for one tanically related to the weed plants which infest fields month. Readings on emergence of weeds and crops are in which crops are grown. then made and compared with untreated flats.

The activity of the pre-emergence herbicides embod- 1n the tables which follow, the radicals listed under ied herein is observed in all types of soils and under varthe heading R are understood to be the same as the ious environmental conditions which can change the group R in the following structural formula: response of the crop to a given chemical. In the tables that follow, examples are set forth to illustrate the method of using the invention and are not intended to limit the scope of the method. Cl Cl HERBICIDAL EVALUATIONS I O-CH C Representative compounds embodied in this mven- N 2 RZOR TABLE I Pre-emergence Percent Kill Dosage in Barnyard Crab Wild Downy R lbs/acre grass (l) grass (2) Lambsquarter (3) Amaranthus (4) Oats (5) Brome (6) Phenyl l V 0 5O 0 0 Allyl 0.5 100 90* 90* 0 0 l0 100 100 100 80 100 2 100 100 W0 0 90 l 100 100 95 30-0 -0 Ethyl l0 I00 100 100 40 100 2 I00 I00 100 O 90 l 80 100 100 0 50 0.5 100 0 0 Benzyl l 9O 60* I00 0 I0 90 100 100 0 5 50 I00 100 0 2 40 100 90 0 0.5 0 I00 8O 0 Methyl l0 lOO I00 100 20-40 2 80 0 Propyl l0 I00 100 20 10 I00 100 100 60 2 90 90 80 0 2 so 80 40 0 2 I00 100 60 0 l 100 100 40* 0 Butyl l0 I00 100 100 I0 10 100 I00 100 0 2 2 40 60 0 Dodecyl l 0 loo l 00 100 0 l0 100 I00 l0() 0 2 100 100 I00 0 2,3-dichloropropyl 2 100 70 I00 0 10 100 100 100 20 TABLE I-Continued Pre-emergence Percent Kill Dosage in Barnyard rab Wild Downy R lbs/acre grass (l) grass (2) Lambsquarter (3) Amaranthus (4) Oats (5) Brome (6) 2,2.3-trich- Ioropropyl 2 I I00 0 I00 I00 I00 20 I00 100 I00 0 stunted l Echinmhlua rrusgulli (2) Digilaria sanguinali: (3) Cllelmpndium allrim 4) Amuranllm: relmflarus (5) Arena falua 6) Bran: n't'mmnl TABLE II Dosage in Crop Injury Weed Control R lbs/acre Corn Sugar beet Crab grass" Pig Weed n-propyl 0.5 0 0 I00 50 n-butyl 2 6O 60 2.3-dichloropropyl 0.5 0 0 I00 I00 Control 0.25 80 I00 I00 Digilania .ranguimrlis Aumrunlhirs rum/Icarus TABLE III thy is the high activity shown by these compounds. Individual compounds exhibit high activity even at the Dosage in Crop Injury Weed Control rate of 0.5 or I pounds per acre, and all are active at R lbs/acre Wheat Barley Foxtail Pig Weed dosages of lo pounds per acre.

g-propyl 0.5 0 0 98 98 Table V shows high pre-emergence activity where R ziifg s g2 2 62 is cyclohexyl at dosages of l and 2.5 lbs/acre. General Method Same as for Table II except weed seed is incorporated into the soil instead of seeding on surface.

"' Selaria spp '3.S-dichloro-2-pyridoxyacetic acid.

Table I shows the ge'neral'pre-emergence activity of contact herbicidal activity is shown on bean plants at 5 to 10 lbs/acre.

the compounds of this invention. Particularly noteworcompounds.

Inactive compounds of structure Cl TABLE IV Percentage Pro-emergence Kill Dosage in Crab Wild Downy X lbs/acre Grass Lambsquarter Amaranthus Oats Brome (C,H,),N l 0 0 0 0 0 I0 80 I00 20 0 C,H,0s 10 100 50 I00 30 0 5 0* 0* 0* 0 0 C,H SO, 5 0 0 0 0 0 I0 50 50 80 50 0 4-methoxy phenoxy I0 0* 0 0 5 0 0 0 0 4-tolyloxy I0 0 0 0 0 0 2,4-dichlorophenoxy I0 0 0" 0" 0 0 4-nitrophenoxy l0 0 0 0 0 0 4-chlorophenoxy I 0 l0 0 0 5 60* 50 0 0 Stunted.

Hcrbicidal Activity of 3.5DlCHLORO-2-(CYCLOHEXYLOXYETHOXY)PYRlDlNE PREEMERGENCE lbs./ Red Wild Acre M ustard Root Foxtail C rabgrass Oat Ryegrass 5.0 100K 100K IOOK 100 g 100 2.5 100K 100K 100K 100K 1.0 SOl 90] 100K 90! K Percent Kill I Percent Growth Inhibition CONTACT Bean Plants Tables II and lll, set forth the data showing the selectivity of compounds embodied in this invention. The control compound, shown for comparison, is an active pre-emergence compound but fails to exhibit selectivity in controlling weed seeds while permitting crop seeds to germinate. The claimed compounds, on the other hand, exhibit good weed control and also permit the crop seeds to germinate. This feature adds to the overall usefulness of the claimed compounds because the pre-emergenceactivity of the composition embodied herein may be utilized both before and after sowing crop seeds. The pre-emergerice activity of these compounds is shown using the compound alone. However, these compounds may be formulated with other herbicides in order to obtain additional activity against weed seeds which may be partially .resistant to the compounds of this invention. This partial resistance may result either because an insufficient amount of the compound is applied or because the weed seed is only partially affectedregardless of the amount applied.

In addition, it may be desirable to formulate the compound of this invention withherbicides having other activity, e.g., post emergence activity. These variations in utilizing the invention are known to those skilled in the art.

We claim:

1. In the pre-emergence herbicidal treatment of crops the improvement which comprises applying to weed seeds a weedphytotoxic amount of a 3,5-dichloro-2-pyridoxyethyl hydrocarbon ether having the structure 'or alkynyl having 3 or 4 carbon atoms, chloroalkenyl or chloroalkynyl having 3' or 4 carbon atoms, cyclohexyl, phenyl or benzyl with a proviso that each chloro compound contain from 1 to 6 chlorine atoms.

2. The method according to claim 1 wherein the 3,5- dichloropyridoxyethyl hydrocarbon ether is 3,5- dichloro-Z-[2-(propoxy)ethoxy]pyridine.

3. The method according to claim 1 wherein the 3,5- dichloro-pyridoxyethyl hydrocarbon ether is 3,5- dichloro-2-[2-(dodecyloxy)ethoxy]-pyridine.

4. The method according to claim 1 wherein the 3,5- dichloro-pyridoxyethyl hydrocarbon ether is 3,5- dichloro-2-[ 2-(2,3-dichloropropoxy)-ethoxy]pyridine.

5. The method according to claim 1 wherein the 3,5- dichloropyridoxyethyl hydrocarbon ether is 3.5- dichloro-2-[2-(2,2,3-trichloropropoxy)ethoxy]pyridine.

6. The method according to claim 1 wherein the 3,5- dichloropyridoxyethyl hydrocarbon ether is 3,5- dichloro-2-[2-(cyclohexyloxy)ethoxy]pyridine.

7. The method according to claim 1 wherein the amount of the 3,5-dichloro-2-pyridoxyethyl ether applied to the soil is in the range of from about 0.1 to about 10 pounds per acre.

8. The method according to claim 1 wherein the amount of the 3,5-dichloro-2-pyridoxyethyl ether applied to the soil is in the range of from about 0.1 to about 2 pounds per acre.

9. The method of claim 1 wherein the 3,5-dichloropyridoxyethyl hydrocarbon ether is 3,5-dichloro-2-[(2- benzyloxy)ethoxy]pyridine.

UNITED STATES PATENT OFl'i-(IE CERTIFllL-XTE 0F CORREC'IION- latent No. 318941862 D d Iuly 15, 1975 Inventor) Reginald L. Whitaker and Herbert Q. Smith It is certified that error appears in theabove-identified patent and that said Letters Patent are hereby corrected as shown below:

Example 8, column 5, line 29, delete "2h, .30u" and insert Example 8, column 5, line 30, delete "Oc, 60.64S' Oh, 8.16$"

and insert in its place C, 60.64 H, 8.16

Signed and Scaled this thirtieth Day of September1975 [SEAL] Arrest:

RUTH C. MASON C. MARSHALL DANN Ancslmg Ojj'icer Commissioner of Iurenrs and Trademarks 

1. In the pre-emergence herbicidal treatment of crops the improvement which comprises applying to weed seeds a weedphytotoxic amount of a 3,5-dichloro-2-pyridoxyethyl hydrocarbon ether having the structure
 2. The method according to claim 1 wherein the 3,5-dichloropyridoxyethyl hydrocarbon ether is 3,5-dichloro-2-(2-(propoxy)ethoxy)pyridine.
 3. The method according to claim 1 wherein the 3,5-dichloro-pyridoxyethyl hydrocarbon ether is 3,5-dichloro-2-(2-(dodecyloxy)ethoxy)-pyridine.
 4. The method according to claim 1 wherein the 3,5-dichloro-pyridoxyethyl hydrocarbon ether is 3,5-dichloro-2-(2-(2,3-dichloropropoxy)-ethoxy)pyridine.
 5. The method according to claim 1 wherein the 3,5-dichloropyridoxyethyl hydrocarbon ether is 3,5-dichloro-2-(2-(2, 2,3-trichloropropoxy)ethoxy)pyridine.
 6. The method according to claim 1 wherein the 3,5-dichloropyridoxyethyl hydrocarbon ether is 3,5-dichloro-2-(2-(cyclohexyloxy)ethoxy)pyridine.
 7. THE METHOD ACCORDING TO CLAIM 1 WHEREIN THE AMOUNT OF THE 3,-5-DICHLORO-2-PYRIDOXYETHYL ETHER APPLIED TO THE SOIL IS IN THE RANGE OF FROM ABOUT 0.1 TO ABOUT 10 POUNDS PER ACRE.
 8. The method according to claim 1 wherein the amount of the 3, 5-dichloro-2-pyridoxyethyl ether applied to the soil is in the range of from about 0.1 to about 2 pounds per acre.
 9. The method of claim 1 wherein the 3,5-dichloro-pyridoxyethyl hydrocarbon ether is 3,5-dichloro-2-((2-benzyloxy)ethoxy) pyridine. 